Fertility history and intentions of married women, China

Abstract Objective To estimate the proportion of married women in China who intend to become pregnant given the country’s pronatalist population policy and to investigate fecundity, with an emphasis on the influence of socioeconomic factors. Methods A nationally representative survey of 12 815 married women aged 20 to 49 years (mean: 36.8 years) was conducted during 2019 and 2020. All completed questionnaires, 10 115 gave blood samples and 11 710 underwent pelvic ultrasound examination. Fertility intention was the desire or intent to become pregnant combined with engagement in unprotected sexual intercourse. We defined infertility as the failure to achieve pregnancy after 12 months or more of unprotected intercourse. We considered an anti-Müllerian hormone level < 1.1 ng/mL and an antral follicular count < 7 as indicating an abnormal ovarian reserve. Findings Fertility intentions were reported by 11.9% of women overall but by only 6.1% of current mothers (weighted percentages). Fertility intention was significantly less likely among women in metropolises (odds ratio, OR: 0.38; 95% confidence interval, CI: 0.31–0.45) and those with a higher educational level (OR: 0.74; 95% CI: 0.62–0.88). Overall, 18.0% had experienced infertility at any time and almost 30% had an abnormal ovarian reserve on assessment. An abnormal ovarian reserve and infertility were less likely in women in metropolises (P < 0.05) but more likely in obese women (P < 0.05). Conclusion The willingness of Chinese married women to give birth remained low, even with relaxation of the one-child policy.


Introduction
Fertility rates have been on the decline globally, with recent reports predicting that 23 countries will observe the halving of their population by the end of the century. 1 Although a smaller population may be advantageous for the environment, an aging population presents other challenges to socioeconomic well-being. 2 A key reason for the decline in fertility rates could be people prioritizing their education and careers, combined with the wide availability of contraception. 3,4However, poor fecundity could be equally responsible for the low birth rate.
Previous studies indicate that an increasing number of couples encounter challenges in achieving pregnancy. 5,6Infertility has been estimated to affect 8% to 12% of reproductiveaged couples worldwide. 7In light of the trend towards delayed parenthood, fertility tests are becoming more important in reproductive counselling, particularly when recommending fertility treatment.However, most existing evidence on infertility has been derived solely from questionnaire-based surveys, from which it is difficult to draw clear conclusions about the fecundity of women of reproductive age in general.
Globally, a large percentage of infertile women live in China -one of the most densely populated countries. 8However, infertility has long been overlooked due to the growing size of the Chinese population and the country's family planning policy. 9In 2013, China started to relax its one-child policy to help cope with an aging population and to counter very low fertility.Despite the government enacting a series of policies that targeted married women of childbearing age who had had a previous delivery, 10 the total fertility rate in the country dropped to 1.3 children per woman in 2020. 11In addition, the total fertility rate fell further to 1.15 children per woman in 2021 because of the impact of the coronavirus disease 2019 (COVID-19) pandemic.In this context, detailed data on fertility intention and fecundity in the general population are essential for developing evidence-based policies.
The aim of our study was to bridge the evidential gap on fertility intention and fecundity in China by analysing data from the last iteration of the China fertility survey of mar-Bull World Health Organ 2024;102:244-254| doi: http://dx.doi.org/10.2471/BLT.23.289736   Qin Li et al.Fertility history and intentions of Chinese women ried women, which investigated fertility behaviour and collected information on laboratory and ultrasound markers of fecundity.In particular, we estimated the proportion of married Chinese women who wished to become pregnant in the context of the country's more relaxed population policy, studied their fecundity (i.e.infertility and ovarian reserve), and assessed how pregnancy desire and fecundity were influenced by sociodemographic factors.In addition, we intended to provide baseline data on fertility intentions before the onset of the COVID-19 pandemic.

Methods
3][14] The 2020 survey took place between January 2019 and December 2020.We used a multistage, stratified, sampling method to select a representative sample of women of reproductive age.First, we selected 15 provinces with experience of fertility surveys from the 31 provinces of mainland China (Fig. 1): (i) Fujian, Guangdong, Hainan, Shanghai and Zhejiang in south-east China; (ii) Guizhou, Sichuan and Yunnan in south-west China; (iii) Beijing, Hebei, Henan, Hubei, Shanxi and Tianjin in central China; and (iv) Liaoning in north-east China.We did not include north-west China due to the difficulty of fieldwork in this area.Second, we divided all townships or districts in each province into nine strata according to their degree of urbanization and population size, and selected three townships or districts from each of the highest, middle and lowest strata.Third, we used a random sampling method to select two to four villages or residential areas in each township or district according to their representativeness (i.e.urban or rural location and population size), and to the number of trained interviewers available in each province.In each selected village or residential area, 100 married women aged 20 to 49 years who had been resident for at least six of the previous 12 months before the survey were invited to participate.The sample size met generally recommended requirements for precision in a complex survey design.All participants signed informed consent forms.
Each survey participant completed a questionnaire on: (i) demographic characteristics; (ii) socioeconomic status; (iii) the lifestyle habits of the women and their partners; and (iv) reproductive health.Then they underwent a free medical evaluation, which included: (i) a physical examination; (ii) body mass index assessment; (iii) blood pressure measurement; (iv) a gynaecological examination; (v) a blood test to determine reproductive hormone levels; and (vi) a pelvic ultrasound examination of the uterus and ovaries.Pelvic ultrasound examinations were scheduled to avoid menstrual bleeding. 12,13All study investigators completed a training programme, and qualified clinical staff were trained to obtain blood specimens and perform pelvic ultrasound examinations according to a standard protocol.The survey was approved by the research ethics committees at all participating centres and by the Peking University Third Hospital Ethics Board (protocol 2019SZ-054).

Outcomes
Fertility intention has previously been defined in several ways, which generally reflect desires, attitudes or behaviours. 15e assessed fertility intention by ask-

Research
ing the question, "Are you trying to get pregnant now?" Then we classified fertility intention according to whether the woman had the desire or intent to become pregnant and had had unprotected sexual intercourse in the year before the survey visit.Infertility is defined by the International Committee for Monitoring Assisted Reproductive Technologies and the World Health Organization (WHO) as the failure to achieve a pregnancy after 12 months or more of regular unprotected sexual intercourse. 16n the 2020 China Fertility Survey of Married Women, participants who had experienced any 12-month period when they tried to become pregnant but had not conceived, or who took more than 12 months to conceive, were considered infertile, regardless of whether they had children or not.In addition, we also considered participants who underwent assisted reproduction treatment to achieve pregnancy as infertile.Women who did not report having children at the time of survey were defined as childless, regardless of whether they had given birth or not.
][19] In this epidemiological study, we assessed ovarian reserve by measuring the serum anti-Müllerian hormone level and by counting the number of antral follicles in ovarian tissue during pelvic ultrasonography.An abnormal ovarian reserve was defined as an anti-Müllerian hormone level less than 1.1 ng/mL and an antral follicle count less than seven. 19

Statistical analysis
We calculated outcome estimates using sampling weights and post-stratification weights.For each stratum in the sampling process, the sampling weight equalled the reciprocal of the relevant sampling probability.Post-stratification weighting was based on age, with a standardized population derived using data from the sixth national population census in 2010. 20Taylor series linearization was used to estimate standard errors and to determine 95% confidence intervals (95% CIs) for prevalence estimates.Odds ratios (ORs) and 95% CIs for fertility intention were estimated for various sociodemographic characteristics using a multivariate logistic regression model.Logistic regression models were also used to estimate age-adjusted ORs for infertility; childlessness; and an abnormal ovarian reserve for various sociodemographic, reproductive and health characteristics.We also conducted a sensitivity analysis among women surveyed before 1 January 2020 to assess the influence of the COVID-19 pandemic.All statistical tests were twosided and a P-value under 0.05 was considered significant.All analyses were performed using R version 3.4.2(The R Foundation, Vienna, Austria).

Results
In total, 13 508 married women were interviewed between January 2019 and December 2020.After excluding 408 women younger than 20 or older than 49 years at the time of the survey visit, and 285 whose fertility condition was unknown (Fig. 2), 12 815 women (mean age: 36.8 years) were included in the analysis (Table 1).As 315 women were voluntarily childless, only 12 500 of the 12 815 participants had previously attempted to conceive.
After applying weighting, we estimated that 11.9% of women reported trying to become pregnant at the time of the survey visit (Table 2).There was a significant decline in fertility intention with advancing age (P < 0.05), with 9.3% of 2731 women aged 35 to 39 years still trying to become pregnant.Among 2290 childless women, 25.4% were trying to become pregnant at the time of the visit.In contrast, of the 10 453 women reporting having one or more children, only 6.1% wanted to conceive another.Fertility intention was significantly lower among the 3453 women residing in a metropolis than among the 9362 not in a metropolis (OR: 0.38; 95% CI: 0.31-0.45);and among the 7223 women with an education higher than primary school than in the 5449 with primary education only (OR: 0.74; 95% CI: 0.62-0.88).In addition, women with a higher body mass index were more likely to report fertility intention (P < 0.05).Findings were similar in a sensitivity analysis conducted to investigate the impact of the COVID-19 pandemic on fertility intentions, which Table 3 shows the estimated odds of infertility and childlessness among the 12 500 women who tried to become pregnant, according to sociodemographic characteristics and ovarian reserve.Of these women, 2237 reported they had unsuccessfully tried to conceive spontaneously for 12 months or more in the past.The weighted prevalence of infertility was 18.0% (95% CI: 16.9-19.0).As indicated by age-adjusted odds ratios, the prevalence of infertility was significantly lower among women who were living in a metropolis (P < 0.05), and tended to be lower in those who had a high annual household income or a high educational level.In contrast, the prevalence of infertility was higher among obese women (P < 0.05), defined as those with a body mass index of 28 kg/m 2 or more.
Overall, 2209 of the 12 500 women who had previously attempted to conceive were childless at the time of the survey (weighted prevalence: 29.1%; 95% CI: 27.0-30.0;Table 3).The prevalence of childlessness declined significantly with increasing age (P < 0.05): it was 7.1% in women aged 35 to 39 years, compared with 4.6% in those aged 40 to 44 yearsy and 5.2% in those aged 45 to 49 years.As indicated by ageadjusted odds ratios, the proportion of women who were childless was significantly higher among urban women than among those living in rural locations, among women with a higher educational level and among women with a body mass index of 18.5 kg/m 2 or less (P < 0.05 for all).In addition, women with an abnormal ovarian reserve had a significantly elevated risk of being childless (P < 0.05).
Table 4 shows the estimated odds of an abnormal ovarian reserve among the women surveyed, according to sociodemographic characteristics.Of the 10 155 participants who underwent a blood test, 3382 had an anti-Müllerian hormone level under 1.1 ng/mL (weighted prevalence: 30.4%; 95% CI: 28.9-32.0).In addition, of the 11 710 participants who underwent pelvic ultrasound examination, 3551 had an antral follicle count less than seven (weighted prevalence: 25.8%; 95% CI: 24.7-27.0).We observed that the ovarian reserve declined significantly with increasing age (P < 0.05).In particular, the prevalence of an abnormal ovarian reserve As indicated by age-adjusted odds ratios, the proportion of women with an abnormal anti-Müllerian hormone level was significantly lower in those who lived in a metropolis, had a higher educational level or had a higher annual household income (P < 0.05 for all).However, no significant association was found between the antral follicle count and any socioeconomic characteristic.The prevalence of an abnormal ovarian reserve was significantly higher in obese women (P < 0.05).

Discussion
In this representative sample of married Chinese women of reproductive age, 11.9% overall reported fertility intentions.The proportion was only 6.1% in women who had already given birth to one or more children.In addition, 18.0% had experienced infertility and almost 30% had an abnormal ovarian reserve at the time of the survey.These findings can help guide a re-examination of population policy in China.Almost all previously available data on fertility intentions have been based on demographic indicators, such as the ideal number of children or intended family size, 15 which has limited our understanding of desired fertility.Our study, which used individual epidemiological data, found that 25.4% of women who had no children were trying to conceive compared with 6.1% of women who already had children.A 2011 study revealed that 74% of childless women aged 20 to 40 years in France and 85% of similar women in Italy intended to have a child.Moreover, 62% of mothers with one child in France and 53% in Italy intended to have a second child. 21In addition, a survey conducted in Australia in 2011 estimated that 21.8% of women aged 18 to 41 years had a strong desire to conceive. 22Although the age compositions of the women sampled in these studies differ from those in our survey, the numbers indicate that, even with a relaxed population policy, the proportion of Chinese women of childbearing age who want to bear children is low.
Generally, the predominant reason for a low fertility rate is a decline in fertility intentions.In China, the traditional division of labour in families persists: men typically serve as breadwinners, while women assume the role of primary caregivers.Under the system of public ownership, work-family conflicts were relatively well reconciled for urban working women. 23However, with economic globalization, an increasing number of women in recent decades have prioritized their education and career, which has resulted in a widespread trend towards delayed motherhood. 24Moreover, faced with a scarcity of childcare provision and the increasing cost of raising children (e.g. investment in education) during the transition to marketization, 23 a substantial proportion of young citizens decided to postpone becoming parents, or to opt for fewer children, or both.These factors could explain the low fertility intentions among women with a high socioeconomic status that we observed.
Poor fecundity is another reason for low fertility.In our study, we assessed the fecundity of Chinese women of reproductive age using biological markers and found that almost a third Fertility history and intentions of Chinese women had an abnormal ovarian reserve.A low anti-Müllerian hormone level appears to be correlated with a low number of antral follicles and is indicative of a low ovarian reserve, which is, in turn, associated with poor fertility. 19The anti-Müllerian hormone level and the antral follicle count are less influenced by the menstrual cycle than levels of other re-productive hormones related to fertility.Consequently, in large-scale epidemiological surveys, these two markers can give a better indication of the potential fertility of the general population.
Although the reasons for the general reduction in ovarian reserve are not fully understood, it is widely accepted that the life stress and envi-ronmental pollution accompanying industrialization could be associated with premature ovarian aging. 19One possible result of an accelerated general decline in ovarian reserve is that a woman who has an abnormal ovarian reserve at an early age could have an increased risk of infertility, pregnancy loss and even adverse birth outcome. 25

Research
Combined with the trend of delayed motherhood, these changes in ovarian reserve suggest that a large well-educated section of the Chinese population may be affected by infertility, have poor responses to fertility treatment and will even remain childless in the future.
In a previous study in 2010, we found that the prevalence of infertility in China was 15.5%. 12Following the easing of the one-child policy in 2015, some older mothers attempted to have a second child, which may have increased the recorded prevalence of infertility.In the present study, we reported a prevalence of 18.0% after adjusting for sampling weights and the age composition of the population.This rate was slightly higher than that observed in developed countries like Finland (16.0% in 2002)  and Norway (12.7% in 2006), 26,27 as well as in China a decade ago. 12More worrying is the number of women who remain unable to conceive. 5In 2020, 56% of infertile couples sought fertility treatment in China. 28However, the live birth rate with assisted reproductive technologies hovers around 25% in China, Europe and the United States of America. 28Consequently, not only can it be expensive to treat infertility, but the resulting unintentional childlessness imposes a substantial burden on both individuals and society.In our study, less than one fifth of married Chinese women under 30 years of age expressed fertility intentions at the time of the survey.Moreover, fertility intention was even less common among women living in a metropolis and in those with a higher educational level.The difficulty of combining motherhood and employment appears to be responsible for delaying, or giving up, having a child.On the other hand, although women with a relatively low socioeconomic status were more likely to have fertility intentions, they were also more likely to have an abnormal ovarian reserve.Hence, the cause of low fertility can differ among various demographic groups.For newly industrialized countries with low fertility rates, belowreplacement fertility, rapidly aging populations and looming labour shortages, it is critically important that policies are introduced to improve women's reproductive health and the living standards of families with children.Infertility and unintended childlessness in women of childbearing age could be alleviated by monitoring ovarian reserves and devising a childbirth plan.
In our study, we also observed that obesity was associated with fertility intention, infertility and an abnormal ovarian reserve.Evidence suggests that being obese can lead to a decrease in the number and volume of oocytes, thereby inducing hormonal dysfunction and, potentially, irregular ovulation or even anovulation. 29A recent study of 2.3 million Chinese couples who wanted to conceive found that the pregnancy rate was 19% lower in obese women than in those with a normal body mass index. 30Obesity can be a manifestation of the metabolic complications of polycystic ovary syndrome, and there is an indication that obese patients with the syndrome have a more severe phenotype than those with a normal weight. 31verweight and obesity are increasingly prevalent and have extensive adverse consequences. 32Consequently, lifestyle interventions to achieve a healthy weight are of great importance, both in themselves and for intergenerational health.
Our study had several limitations.First, information on reproductive history was collected retrospectively in the survey.Even though we designed a series of logically related questions to determine reproductive history, and excluded questionnaires with logical errors from our analysis, the estimated infertility rate may have been influenced by recall bias, particularly when the follow-up time was long. 33Second, in the villages and streets selected, the response rate among young women may have been low because many were studying or working in another city.Consequently, potential selection errors should be considered when interpreting our prevalence rates.Nevertheless, these limitations were unlikely to have distorted our results because our sample size was large and we calculated ageadjusted rates.
Our definitions of fertility intention and infertility should be noted.Fertility intention at the time of survey was conceptualized as the desire or intent to become pregnant combined with a reported engagement in unprotected sexual intercourse.This definition may have resulted in an underestimate of fertility intention compared with that derived from demographic indicators, such as the ideal number of children and intended family size.Furthermore, it is noteworthy that participants were visited by medical personnel between January 2019 and December 2020.The outbreak of the global COVID-19 pandemic was officially declared by WHO on 11 March 2020.As the global pandemic had the potential to influence fertility intentions, we conducted a sensitivity analysis in which we excluded 878 participants who were visited after 1 January 2020.We found that our conclusions were unlikely to have been substantially altered by the pandemic.
Finally, unlike studies that investigated infertility at a specific point in time (e.g. in the preceding year), which can minimize potential recall bias in reproductive epidemiology studies, 8 we used infertility at any point in a woman's lifetime to estimate the overall burden of infertility among women of childbearing age.
In conclusion, the willingness of Chinese married women to give birth continues to be low despite the government's relaxation of the one-child policy in 2013.

Fig. 1 .
Fig. 1.Provinces included in the survey of fertility intention and fecundity in married women, China, 2019-2020

Body mass index in kg/m 2
IQR: interquartile range; SD: standard deviation.a The values listed are for raw data, before sampling and post-stratification weighting.b All women surveyed were aged between 20 and 49 years.c The metropolises included in the survey were Beijing, Guangzhou, Shanghai and Shenzhen.d During 2019 and 2020, 1 yuan was equivalent to 0.14 United States dollars on average.Bull World Health Organ 2024;102:244-254| doi: http://dx.doi.org/10.2471/BLT.23.289736Qin Li et al.Research rose sharply after the age of 35 years.

Table 2 . Factors associated with fertility intention, survey of fertility intention and fecundity in married women, China, 2019-2020 Survey participants' characteristic % of participants trying to conceive (95% CI) a Likelihood of trying to conceive, OR (95% CI) b
Odds ratio were estimated using a multivariate logistic regression model that included all covariables listed in the table.c The metropolises included in the survey were Beijing, Guangzhou, Shanghai and Shenzhen.d During 2019 and 2020, 1 yuan was equivalent to 0.14 United States dollars on average.Bull World Health Organ 2024;102:244-254| doi: http://dx.doi.org/10.2471/BLT.23.289736Qin Li et al.
CI: confidence interval; NA: not applicable; OR: odds ratio.a The figures listed are for weighted proportions based on sampling weights and post-stratification weights.b

Table 3 . Factors associated with infertility and childlessness, survey of fertility intention and fecundity in married women, China, 2019-2020
CI: confidence interval; NA: not applicable; OR: odds ratio.aInfertilityincludedprimaryandsecondaryinfertility.bThefigureslistedareforweightedproportions based on sampling weights and post-stratification weights.cWeestimatedORsusing a logistic regression model that included adjustment for age.dThemetropolisesincluded in the survey were Beijing, Guangzhou, Shanghai and Shenzhen.eDuring2019and 2020, 1 yuan was equivalent to 0.14 United States dollars on average.fWedefinedan abnormal ovarian reserve as an anti-Müllerian hormone level less than 1.1 ng/mL and an antral follicle count under seven.Bull World Health Organ 2024;102:244-254| doi: http://dx.doi.org/10.2471/BLT.23.289736QinLi et al.

Table 4 . Factors associated with an abnormal ovarian reserve, survey of fertility intention and fecundity in married women, China, 2019-2020 Survey participants' characteristic Abnormal ovarian reserve Anti-Müllerian hormone level < 1.1 ng/mL (n = 10 155) a
Of the 12 815 survey participants, 11 710 underwent a pelvic ultrasound examination.cThefigures listed are for weighted proportions based on sampling weights and post-stratification weights.dWeestimated odds ratio using a logistic regression model that included adjustment for age.e The metropolises included in the survey were Beijing, Guangzhou, Shanghai and Shenzhen.
CI: confidence interval; NA: not applicable; OR: odds ratio.a Of the 12 815 survey participants, 10 155 had a blood test for reproductive hormones.b f Fertility intention was the desire or intent to become pregnant combined with engagement in unprotected sexual intercourse.Bull World Health Organ 2024;102:244-254| doi: http://dx.doi.org/10.2471/BLT.23.289736Qin Li et al.Fertility history and intentions of Chinese women Better targeted population stimulus policies may be needed to boost China's low fertility rate.■ Bull World Health Organ 2024;102:244-254| doi: http://dx.doi.org/10.2471/BLT.23.289736Qin Li et al.